The invention relates to an arching mechanism, particularly for a backrest for a vehicle seat or seats for office and home furniture, respectively seats of all kind, as well as for use particularly in medical or orthopaedic devices and apparatus, such as corsets or arch supports, in scaffoldings or casings, for the production of hulls, etc.
When for instance the arching of a backrest in adjusted, usually the apex of its convexity wanders according to the construction type of the arching mechanism over the height of the backrest, always remaining the same. It does not adjust sufficiently to the constantly changing curvature of a more or less curved spinal column, or to a stretching of the spinal column which is medically recommended or desired by the user. In constructions with shell seats, usually the lateral support diminishes with increased arching.
The EU-B-37656 shows a restraining frame for a motor vehicle seat, wherein a support piece is suspended by springs. The support piece consists of two lateral parts connected to the frame by springs and mutually connected by cross elements. There is a centrally located adjusting shaft which can be actuated by a hand wheel, the shaft running through so-called engagement devices, which in turn are connected to the outermost points of the lateral parts via flexible connection elements. When the hand wheel is turned, an arching of the support part is supposed to result, whereby basically in the beginning only an expansion of the springs occurs. This type of construction affords support to only a few vertebrae; the vertebrae lying above and below do not get the same strong support. A freely suspended insertion of the support part in the backrest or a construction wherein the support is suspended in the upholstery is not possible.
The DE-OS 2304703 shows a backrest wherein a plate having straps arranged oppositely to each other can be arched via mutually engaged guide rails. The entire plate is height-adjustable by means of a rocker lever.
The EU-A1-322535 shows a backrest with an upper and a lower support strap which are interconnected by a vertical, flexible strap and a spring tensioned between them, whereby an adjusting shaft engages via a gear in the lower support strap, in order to achieve an arching of the backrest by bending the flexible strap.
Further, backrests made of foam material are known, which are supposed to adjust to the shape of the spinal column.
Another example is shown by DE-CS 3440846 which discloses an automobile seat whose backrest comprises a frame and a plate received in the frame. The plate is provided with vertically extending longitudinal slits in which a lumbar-support device is movable. The lumbar support can be adjusted by a hand wheel through a shaft linked onto the frame to vary its stiffness and to move it vertically.
The lumbar support is directly connected with the frame. As a result, all vibrations imparted by the road to the vehicle are fully transmitted to the back of the driver.
The known mechanism do not permit any accommodation to changed or changing curvatures of the spinal column. For instance, during long car trips, the curvature of the spinal column alters greatly as a result of the required holding work, when the total weight of the upper body must be supported based on this disadvantageous position (hand stretched out towards the steering wheel). This muscle work, respectively holding work in order to keep the body upright under conditions of improper or insufficient support has to be performed entirely by the musculature and the skeletal system, and thus logically leads to considerable exhaustion, as well as muscle stress. The involved muscles require for this work up to 40 times more blood, respectively 40 times more energy, compared to an anatomically supported upper body (whose muscles do not have to perform any holding work).
The support, respectively holding work must be performed by the arching mechanism and namely for all spinal columns (whose curvatures are as varied as human facesxe2x80x94and which in addition, are constantly altered from hour to hour due to tiredness, exertion and the required holding workxe2x80x94the height of a person decreases from morning to evening be approximately 2 to 4 cm, and the spinal curvature changes in this time period by up to 10 cm). Thus, an optimal arching mechanism has to act in a differentiated manner so that for instance when used in a backrest, it can suitably support any shape of back, i.e. at least threefold and with variable strength, as follows: 1. very strongly and stably in forward direction in the pelvic area (against the backward tilting of the pelvis), 2. somewhat gentler but equally firm radially and vertically in order to support each vertebra in the lower-back (lordosis) area and 3. essentially stronger and vertically in an upward direction in the pectoral area under the shoulders against the weight of the upper body.
The additional support for the neck area can be a further requirement.
Once the arch is set and adjusted to the shape of the spinal column, it is naturally not allowed to change its shape even under fully exerted pressure, in order to insure full support independently from the momentary curvature of the spinal column of the user.
The at least support required from an ergonomically optimal backrest can not be offered at all or only insufficiently by the known methods.
It is therefore the object of the present invention to avoid the above-mentioned drawbacks and to create an ergonomically curvable and height-adjustable arching mechanism with a wide spectrum of application and which, when used as a lordosis support insures a multiple, at least a triple support.
The object of the invention is attained due to the fact that in its upper and/or lower region, a general pressure element engages at least one traction element connected with a tension element or a pressure mechanism, and that when the tension device or the pressure mechanism is actuated, the curvature caused by the mechanism occurs so that the apex of its convexity is maintained or is displaced with respect to its relative elevation.
The relative position of the apex of convexity is thereby considered either with reference to the used frame, or a seat or even the apex of the lordosis of the person, i.e. when the person moves in the seat thereby altering the lordosis, the apex of the convexity of the mechanism has still to remain always adjusted to the lordosis.
Another embodiment of the invention comprises a frame and therein inserted pressure elements actuatable by at least one adjustment device, preferably pressure strips or surfaces, and the vertically running segments of the frame are length-variable over at least one adjustment device.
In a further embodiment variant of the invention, the arching mechanism comprises an arching body, which is slitted, overlapping or shaped like bellows and at least at these points traction elements provided with one or several tension mechanisms engage for closing, respectively opening of these areas, whereby a curving of the arching body in each desired, preestablished direction can be achieved.
Further features of the invention can be understood from the dependent claims, the specification and the attached drawing.